Method for cleaning dishes and the like

ABSTRACT

THIS INVENTION RELATES TO A METHOD FOR CLEANING DISHES AND THE LIKE, AND COMPRISES APPLYING TO THE DISHES AN AQUEOUS SOLUTION OF A DISHWASHING COMPOSITION CONTAINING AN AMYLOLYTIC ENZYME PREPARED FROM BACTERIA OR FUNGI TOGETHER WITHA DETERGENT SURFACTANT AND A WATER-SOLUBLE BULIDER SALT. THE COMPOSITION HAS A PH OF 7 TO 9 AT A CONCENTRATION OF 3G. PER LITER IN AQUEOUS SOLUTION.

United States Patent METHOD FOR CLEANING DISHES AND THE L Andries Francke and Karl Ludwig Heinz, Vlaardingen, Netherlands, assignors to Lever Brothers Company, New York, N.Y.

No Drawing. Continuation-impart of application Ser. No. 228,235, Feb. 22, 1972, which is a continuation of application Ser. No. 866,720, Oct. 15, 1969, which is a continuation-impart of application Ser. No. 856,902, Sept. 4, 1969, which in turn is a continuation of application Ser. No. 683,004, Nov. 14, 1967, all now abandoned. This application Apr. 27, 1972, Ser. No. 248,076

Int. Cl. Clld 7/42 US. Cl. 25289 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method for cleaning dishes and the like, and comprises applying to the dishes an aqueous solution of a dishwashing composition containing an amylolytic enzyme prepared from bacteria or fungi together with a detergent surfactant and a water-soluble builder salt. The composition has a pH of 7 to 9 at a concentration of 3 g. per litre in aqueous solution.

This application is a continuation-in-part of our earlier filed application Ser. No. 228,235, filed Feb. 22, 1972, and now abandoned, which is a continuation of our earlier application Ser. No. 886,720, filed Oct. 15, 1969, now abandoned, which in turn is a continuation-in-part of our earlier application Ser. -No. 856,902, filed Sept. 4, 1969, now abandoned, which is a streamlined continuation of Ser. No. 683,004, filed Nov. 14, 1967, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a method for cleaning dishes and the like, comprising applying to the dishes an aqueous solution of a dishwashing composition comprising enzymes. More specifically the present invention relates to a method for cleaning dishes and the like, comprising applying to the dishes an aqueous solution of a dishwashing composition having a pH of 7-9 at a concentration of 3 g. per litre in aqueous solution, said composition consisting essentially of -90% by weight of a detergent selected from the group consisting of an anionic synthetic detergent, a nonionic synthetic detergent and an alkali metal soap, from l80% by weight of a water-soluble alkali metal builder salt, and amylolytic enzymes prepared from bacteria or fungi in an amount such that the composition has an amylolytic activity of 10 -10 maltose units per kg.

Description of the prior art In the cleaning of dishes, plates, pots, pans, cups, etc., the removal of organic soil plays an important part. In particular the satisfactory removal of food residues adhering to the dishes presents considerable difiiculties, the more so when these food residues have dried up. In mechanical and manual dishwashing a soaking step is oftenincluded in order to assist removal of these food residues. However, even after soaking the removal of starch-containing food residues such as those from potatoes, pudding, and of protein-containing food residues such as those from eggs, milk, etc., is still not satisfactory in most cases without applying a scrubbing or agitation step. Moreover, the preliminary soaking is time-consuming.

Commercial dishwashing compositions are normally highly alkaline, the pH being in the order of 11. Such a high alkalinity, however, suffers from several drawbacks. For example, objects of soft metals, such as aluminium,

3,799,879 Patented Mar. 26, 1974 are often subject to attack by such highly alkaline cleaning compositions, which may etch aluminium to a considerable extent. These highly alkaline cleaning compositions also tend to attack the surface of objects made of glass, which results in etched, unsightly surfaces. Highly alkaline cleaning compositions can also cause skin irritation when used for hand dishwashing, particularly on prolonged immersion. The high alkalinity was, however, considered necessary to obtain a satisfactory cleaning'action.

The use of enzymes for general cleaning purposes is well known in the art. Thus, for example, in British patent specification 265,024 it is stated that dirt, found on human clothing, domestic articles and the like, which dirt generally consists largely of albuminous and fatty materials, is far more easily and rapidly removed by cleansing media in the presence of enzymes, that is tryptic enzymes. These cleansing media, however, are highly alkali ne, and suffer therefore from the above-mentioned drawbacks. Incorporation of amylolytic enzymes in these cleansing media is not taught in this specification, and as will be shown later on, the use of amylases in such cleansing media does not yield a beneficial dishwashing effect.

In US. patent specification 1,716,347 a method of washing fabrics with an aqueous detergent-containing liquid in the presence of urea and urease is disclosed, and in US. patent specification 1,970,578 the use of particular nonionic synthetic detergents together with amylases for desizing textile gods is disclosed. None of these publications, however, disclose or teach the use of amylolytic enzymes in a cleaning composition with a pH of 7-9 as a dishwashing composition.

In US. patent specification 3,519,570 a process for making free-flowing, enzyme-containing detergent granules is described, in which the surfaces of base carirer detergent granules -are rendered glutinous with a low melting, liquefiable nonionic surface-active agent, and subsequently powdered enzymes are conglutinated with said glutinous surfaces. These enzymes include proteases, derived from micro-organisms, and amylases, the source of which is not further specified in this specification. According to this US. patent specification, amylases function primarily in acid to neutral systems. In as far as the effective date of this US. patent specification is concerned, it discloses the use of the detergent compositions revealed therein in all cleaning operations, especially in removing soil and foreign materials from textiles and fabrics. It does not disclose, however, dishwashing with a composition which has a pH at 3 g./l. in aqueous solution of 7- 9, a system which is from neutral to alkaline, nor does it disclose the use of amylolytic enzymes, derived from bacteria and fungi. The latter, in contrast with amylases from vegetable or animal origin, are more sensitive to calcium-complcxing agents like sodiumtripolyphosphate, and consequently it is surprising that, neverthelcss, the amylases of bacteria and fungi in the compositions of the invention, which contain calcium-complexing builder salts, are particularly efiicacious in a method for cleaning dishes with an aqueous solution thereof.

SUMMARY OF THE INVENTION In accordance with this invention it has been found that the above-mentioned disadvantages can be significantly reduced, and a significant improvement in soil removal can be obtained by cleaning the dishes and the like with an aqueous solution of a dishwashing composition that consists essentially of a detergent selected from the group consisting of an anionic synthetic detergent, a nonionic synthetic detergent and an alkali metal soap, a watersoluble alkali metal builder salt and amylolytic enzymes,

derived from bacteria and fungi, which composition has a pH of 7-9 at a concentration of 3 g. per litre in aqueous solution. The attack of highly alkaline dishwashing compositions on e.g. glass surfaces is thereby significantly reduced, and in many cases unsightly surfaces of glass articles, cleaned with such a highly alkaline dishwashing composition may be cleaned with a composition of the invention, whereby the appearance of the glass surface is greatly improved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a specific embodiment our invention may be exemplified by a method for cleaning dishes and the like, comprising applying to the dishes an aqueous solution of a dishwashing composition having a pH of 7-9 at a concentration of 3 g. per litre in aqueous solution, said composition consisting essentially of 05-90% by weight of a detergent selected from the group consisting of an anionic synthetic detergent, a nonionic synthetic detergent and an alkali metal soap, 180% by weight of a watersoluble alkali metal builder salt and amylolytic enzymes derived from bacteria and fungi, in an amount such that the composition has an amylolytic activity of -10 maltose units per kilogram. The aqueous solution comprising the above dishwashing composition can be applied to the dishes in manual dishwashing operations or in machine dishwashing operations.

, In manual dishwashing the temperature of the wash liquor will normally be from room temperature to a temperature of about 50 C. The concentration of the dishwashing composition in a wash liquor for manual dishwashing depends on the physical form of the composition, whether liquid or powdered, and generally varies from 2 to 5 g./l. In machine dishwashing the aqueous solution 'with the dishwashing composition can be applied to the dishes during a pre-soaking step, a soaking step or during the main washing step. In general in a machine dishwashing operation the wash liquor containing the dishwashing composition is either heated from room temperature to about 70 0., generally to 55-65 (3., with a rate of 1-4 degrees Celsius per minute, normally about 2 C./minute, or the wash liquor is made up from water of a temperature of 5070 0., usually 60 C., to which the dishwashing composition is added directly.

In general the concentration of dishwashing composition in the aqueous solution is from l-10 g./l., usually about 5 g./l., in machine dishwashing. The washing operation in general may take from 1 minute to about an hour, and is generally from 20-45 minutes.

The detergent in the dishwashing composition can be an anionic synthetic detergent, a nonionic synthetic detergent, or an alkali metal soap.

Examples of anionic synthetic detergents are alkali metal salts of alkyl sulphonic or alkyl sulphuric acids having from 8 to 20 carbon atoms in the alkyl chain; of alkylaryl sulphonic acids with a (I -C alkyl chain and in which aryl is benzene; of sulphonation products of C8020 a-olefins that have been hydrolyzed and neutralized; of hydroxy alkyl methyl taurides wherein alkyl is C -C Further examples of suitable anionic synthetic detergents can be found in Schwartz, Perry and Berch, Surface Active Agents and Detergents, vol. II, 1958, under the heading Anionic Surfactants, which is hereby incorporated by way of reference.

Examples of nonionic synthetic detergents are ethylene oxide condensation products of fatty alcohols with C y-C alkyl groups, of alkyl phenols with C -C alkyl groups, of propylene glycol condensed with propylene oxide, etc. Further suitable examples of nonionic synthetic detergents can be found in the above cited reference Schwartz, Perry and Berch under the heading Nonionic Surfactants.

Examples of alkali metal soaps are the sodium soaps of C -C fatty acids, such as coconut oil, palm oil, fish oil fatty acids, etc. The fatty acids may be natural or synthetic. Further examples can be found in Schwartz, Perry and Berch under the heading Soaps.

In general from 0.5% up to 90% of detergent may be present depending upon the physical state of the composition (powder, aqueous liquid or non-aqueous liquid). For powders and aqueous liquids the amount may be up to 50%, whereas for non-aqueous liquids a higher amount of up to 90% may 'be used.

The compositions to be used in the present invention contain Water-soluble alkali metal builder salts in an amount of up to Water-soluble builder salts form complexes with the water-hardness ions and increase the level of detergency of detergents. Suitable examples of water-soluble builder salts are alkali metal tripolyphosphates, pyrophosphates', alkali metal salts of amino polycarboxylic acidssuch as ethylene diamine tetra-acetic acid, nitrilo triacetic acid, etc. Other suitable water-soluble builder salts can be found in Schwartz, Perry and Berch under the heading Inorganic and Organic Builders.

The composition to be used in the present invention further comprises amylolytic enzymes, derived from bacteria and fungi.

Suitable examples of amylases, derived from bacteria are those produced by the Bacillus species, in particular by strains of B. subtilis. Such amylases are commercially available, e.g. ot-amylase ex Novo Industri A/S, Copenhagen, Denmark; Maxamyl ex Royal Fermentation Industries, Delft, Netherlands; bacterial a-amylase ex Wallerstein Co., New York. Suitable examples of amylases, derived from fungi are those derived from Aspergillus oryzae, Aspergillus niger, A. alliaceus, A. wentii, Penicillium glaucum and the like. Preferably a-amylases, derived from bacteria and fungi, are used in the present invention. Alpha-amylase has proved to be especially suitable for incorporation in compositions to be used in the method according to the present invention; its addition significantly improves and accelerates the removal of food residues from soiled surfaces.

The amount of amylolytic enzymes incorporated in the compositions to be used in the present invention is dependent upon their activity. In general such an amount is incorporated that an activity is obtained of l0 --10 maltose units (M.U.) per kilogram of final product. The amylolytic activity can be determined by the method as described by P. Bernfeld in Methods in Enzymology, vol. I, 1955, p. 149.

For machine-dishwashing a low-sudsing composition is often desired. In that event the composition may contain from 2-10% of a nonionic synthetic detergent, from 40- 60% of an alkaline condensed phosphate, and from 5- 15% of an alkaline silicate. If a medium-sudsing or highsudsing composition is to be used, an anionic synthetic detergent or a mixture of an anionic and a nonionic synthetic detergent may be employed.

It has also been found that a further improvement in the cleaning of soiled dishes is achieved by applying an aqueous solution of a dishwashing composition which contains a mixture of amylolytic enzymes derived from bacteria and fungi and proteolytic enzymes. Soil which also contains protein is thus more effectively removed.

The invention additionally providse a method for cleaning dishes, comprising applying an aqueous solution of a dishwashing composition containing a mixture of amylolytic enzymes, derived from bacteria and fungi, and proteolytic enzymes.

The proteolytic enzymes to 'be used in the method of the invention are preferably also derived from microorganisms such as bacteria and fungi. Examples of suitable proteolytic enzymes are those produced by Bacillus subtilis and specific strains thereof. Such proteolytic enzymes are commercia ly available, e.g. under the trade name Alcalase, a serine protease, ex Novo Industri A/S, Copenhagen, Denmark and Maxatase ex Royal Fermentation Industries, Delft, Netherlands. Other examples of proteases derived from fungi are those pro duced by Aspergillus species, e.g. Aspergillus peptidase.

The amount of proteolytic enzymes to be used according to the invention also depends upon their activity. In general the amount is such that the activity of the enzyme in the final product lies between 5 and 20 Anson units per kilogram of final product. An Anson unit is that amount of proteolytic enzyme, that degrades haemoglobin under the standard conditions as described by M. L. Anson in Journal of General Physiology, vol. 22 (1938), p. 79, with such an initial velocity, that per minute an amount of degradation products is obtained which are not precipitable by trichloroacetic acid, which produces the same color intensity as 1 milliequivalent tyrosine with the phenol reagent.

When a mixture of amylolytic and proteolytic enzymes is used, the ratio in which these enzymes are used is dependent upon their activity. In general the activity of the individual enzymes should lie within the ranges defined above. The temperature at which the compositions may be used according to the invention is dependent upon the enzymes used. When alpha-amylase obtained from micro-organisms is used, the temperature may be as high as 90 C. before the benefit in respect of soil removal disappears.

The compositions to be used in the method of the invention may further contain the usual adjuvants such as sodium silicate, sodium sulphate, lather boosters, such as coconut ethanolamide, soilsuspending agents, such as sodium car-boxymethylcellulose, alkaline or alkaline earth salts, such as sodium bicarbonate, borax, etc., solvents, such as alcohol, hydrotropes, such as urea, bleach precursors and per compounds, such as sodium perborate. Furthermore perfumes, coloring matter etc. may be added if desired.

The term dish where used in this specification is a general one, and is intended to cover other articles such as cups, saucers, pots and pans, and also other hard surfaces such as tiles.

The invention will now be further illustrated by the following examples; in these and elsewhere in the specification references to percentages are to percentages by weight. The amylase in all examples is a-amylase from B. subtilis.

EXAMPLE I Percent Nonyl phenol 14 E0 7.5 Sodium triphosphate 45 Sodium carboxymethylcellulose 1 Sodium sulphate 33 Water, perfume to 100% (pH=8.6).

at temperatures of 20, 40 and 60 C. respectively. The soil removal of this solution was compared with that of an identical solution which also contained 0.19 g./l. of alpha-amylase (16,000 M.U./g.).

The results after soaking for 1 hour are shown in the following table:

Temperature in 0.

Standard solution 20 40 60 Without enzyme..-. 1 1 1 With enzyme 4 4 4 No'rE.Scale: 1=25% of soil removed. 4= Soil completely removed.

6 EXAMPLE n The following composition is suitable for use in dishwashing machines where low-sudsing is required.

Percent Tallow fatty alcohol 25 E0 6 Sodium triphosphate 45 Sodium carboxymethylcellulose 1 Sodium silicate 8 Sodium sulphate 30 Alpha-amylase (16,000 M.U./g.) 5 Water, perfume to (pH=8.5).

EXAMPLE III The following composition is suitable for use in dishwashing where high-sudsing is required.

Water, perfume to 100% (pH=8.6).

Beaker glasses, soiled with aged soil, consisting of milk, rice, flour and egg, were treated with an aqueous solution containing 3 g./l. of the above composition at 40 and 60 C. for 1 hour. The soil was completely removed.

These beaker glasses were also treated under the same conditions with the same solution which, however, did not contain the enzymes. After soaking for 1 hour only 25% of the soil had been removed.

EXAMPLE V Dishes and the like were cleaned with a composition of the invention (B) and with the same composition without enzymes (A), and the results obtained were compared Percent by weight Sodium trlphosphate 42 42 Sodium dlhydrogenphosphate 13 18 Sodium sulphate 4. 4 3. 4 Sodium bicarbonate 37 36 A polyoxyethylene-polyoxypropylene glycol having an approximate molecular weight of 3,000 and containing 40- 50 mol. percent of ethylene oxide 3. 6 3. 6 Benztriamln 01 0. 01 Perfume 03 0.03 Amylase (16,000 M. U./g.) 1- Amylase plus protease (21,000 M. U./g.) plus 0.8 Anson unit 1. 0

Nora-The pH of an aqueous solution of 3 g./l. oteaeh of thee ompositions was 7.6.

The dishes and the like were cleaned in the following way.

In a Bauknecht dishwashing machine the following soiled tableware was cleaned:

4 tumblers, soiled with milk 4 cups, soiled with cotfee and lipstick 6 cups, soiled with tea 6 plates, soiled with a food mixture containing starchy material 6 plates, soiled with a food mixture containing proteins 2 spoons, soiled with a food mixture containing proteins 2 forks, soiled with a food mixture containing proteins 2 knives, soiled with a food mixture containing proteins 2 silver spoons, soiled with a food mixture containing proteins.

The cleaning programmeof the dishwashing machine was:

cold pre-rinsing for 1 minute cleaning at 65 C. for 21 minutes (at 35 C. the dishwashing composition was added) rinsing at 40 C. for 3 minutes rinsing at 75 C. for 22 minutes drying for 1 minute.

This was repeated ten times and the scores of the tests were determined using a scale of 1 to 12, in which the value 8 is the value for water:

1=ideal, spotless 2=very good 3=good 4=slightly soiled 5=for most purposes unacceptable 6=soiled and spotted 7=moderately soiled 8=value obtained with water.

Composition Score- 4.1 3.0. Appearance of glasses Blue Not blue.

EXAMPLE VI The same procedure as in Example V was used with the following compositions:

Percent by weight Sodium phosphate. 43 43 Sodium dihydrogenphosphate- 10 10 Sodium sulphate 8 7 Sodium bicarbonate 26 25 A polyoxyethylene-polyoxyp pylene glycol hav ng an approximate molecular weight of 3,000 and containing 40-50 mol percent of ethylene oxide 4 4 Sodium perborate 6 r 6 Sodium laurate 3 3 Perfume 0. 03 0. 03

Bem r file 0.01 0. 01

Amylase (16,000 M.U./g.) 1. 0

Amylase plus protease (21,000 M.U./g.) plus 0.8 Anson 1 0 N orn.The pH of an aqueous solution 01 3 g./l. oi each of the compositions was 7.6.

The scores obtained were the following:

Composition Score 3.3 2.6. Appearance of glasses Blue Not blue.

EXAMPLE VII The following composition was tested in an identical manner as in Example V:

Percent by weight Sodium bicarbonate l7 Polyoxyethylene-polyoxypropylene glycol having an approximate molecular weight of 3000 and containing 40-50 mol percent of ethylene oxide 7 Percent by Weight Sodium perborate 6 Benztriazole 0.5 Sodium citrate 2.5 Protease (1.5 Anson units/g.) 0.75 Amylase (16,000 M.U./g.) 0.25 (pH-=7.8).

The score was 2.9, the appearance of the glasses was not blue, the cutlery was fine.

EXAMPLE VIII The following composition:

Percent by weight Sodium triphosphate 50 Sodium dihydrogenpyrophosphate 13 Sodium sulphate 3 Sodium bicarbonate n 17 Polyoxyethylene-polyoxypropylene glycol with an approximate molecular weight of 3000 and containing 40-50 mol percent of ethylene oxide 7 Sodium perborate 6 Benztriazole 0.5 Sodium citrate 2.5 a-Amylase (16,000 M.U./g.) 1

(The pH of a 3% aqueous solution was 7.8).

showed a score of 2.9 when tested according to Example V, the appearance of the glasses being not blue, and the cutlery being clean.

EXAMPLE IX The same procedure as in Example V was applied to a highly alkaline dishwashing composition of the following composition:

Percent by weight The score was 3.4, the appearance of the glass was blue, the silver was badly tranished, and the stainless steel objects were not spotless. The objects treated with this highly alkaline cleaner were then cleaned with the following composition in the same way as in Example V:

Percent by weight Sodium triphosphate 50 Sodium dihydrogenphosphate 13 Sodium sulphate 4 Sodium bicarbonate 19 Polyoxyethylene-polyoxypropylene glycol with an approximate molecular weight of 3000 and containing 40-50 mol percent of ethylene oxide 7 Benztriazole 0.5 Sodium citrate 2.5 Protease 1.5 Anson units/ g.) 0.75 Amylase-(16,000 M.U./g.) 0.25 (pH-=7.8).

The score was then 2.9, the glass was not blue any more, the silver was not tarnished and the stainless steel was spotless.

EXAMPLE X In the manner as described in Example V various dishwashing compositions with amylolytic enzymes at different pH values were tested. The compositions are given below:

Composition B C D Percent by weight:

Sodium triphosphate Tetrasodium pyrophosphate Disodium dih'ydrogen pyrophosph Sodium sulphate Sodium carbonate Sodium bicarbonate Polyoxyethylene-polyoxypropylene glycol (approx. moi. weight 8000 and containing 40-50 moi. percent of 10 of a water soluble builder salt selected from the group consisting of alkali metal salts of orthophosphates, pyrophosphates, polyphosphates, silicates and carbonates, and amylolytic enzymes derived from bacteria and fungi in an amount such that the composition has an amylolytic activity of 10 -10 maltose units per kg.

2. The step according to claim 1, wherein the dishwashing composition contains in addition thereto proteolytic enzymes in an amount such that the composition has a proteolytic activity of 5-20 Anson units per kg.

3. In a method for cleaning dishes, the step comprising applying to the dishes an aqueous solution of a dishethy1en5oxide) Washing composition having a pH of 7-9 at a concen- Y -/g-)-- 2J1 tration of 3 g. per litre in aqueous solution, said compH 3 g./l. aqueous solution) 11.0 10.0 9.0 8.0 7.0 15 POSItIOH Consisting n ially of 0.5 to 50% by weight of a detergent selected from the group consisting of an The results of the tests were as follows: anionic synthetic detergent, a nonionic synthetic deter- A B C D E Average dishwashing eflieieney 1. 6 1. 5 1. 3 1. 3 1.3 Removal of starch (pudding from dessert plates) 3. 1 2.1 1. 7 1. 7 1. 9 Cleaning of cutlery (3 types of soil amylaeeous paste). 1. 6 1. 5 1. 2 1.2 1. 1 II-Iodine test (all porcelain items) (determination of residual starch on dishes by iodine test):

Average value of residual starch 3. 6 4. 2 2. 7 2. 1 2. 5 Efficiency residual starch (potatoes). 2. 0 l. 9 1. 7 1.3 1. 4 Etficiency residual starch (pudding)- 5. 2 6. 8 3. 7 2. 8 3. 6 Efficiency redeposlted starch- 1.7 1. 5 1. 2 1. 2 1. 3 IIlFilm formation (percent articles; glass and porcelain ware; measure of discoloration):

N0 film 38 28 22 Film. 85 62 72 78 From the results of these tests it is apparent that the dishwashing compositions of the invention are superior to those with a high pH.

EXAMPLE XI A composition comprising 99.5 parts by weight of a dehydrated ordinary toilet soap having a fat content of 78% and 0.5 part by weight of dried pancreas extract according to British patent specification 265,024 was tested in an identical manner as in Example X. The results were as follows:

This clearly shows the superiority of the compositions of the invention over the composition of the prior art, not only with respect to cleaning efliciency, but also in particular with respect to discoloration of glass.

What is claimed is:

1. In a method for cleaning dishes, the steps comprising applying to the dishes an aqueous solution of a dishwashing composition having a pH of 7-9 at a concentration of 3 g. per litre in aqueous solution, said composition consisting essentially of 05-90% by weight of a detergent selected from the group consisting of an anionic synthetic detergent, a nonionic synthetic detergent and an alkali metal soap, from 1-80% by weight gent and an alkali metal soap, from 1-60 percent by weight of a water-soluble alkali metal builder salt selected from the group consisting of alkali metal salts of orthophosphates, pyrophosphates, polyphosphates, silicates and carbonates, and amylolytic enzymes derived from bacteria or fungi in an amount such that the composition has an amylolytic activity of 10 -10 maltose units per kg.

4. The step according to claim 3, wherein the dish-' Washing composition contains in addition thereto proteolytic enzymes in an amount such that the composition has a proteolytic activity of 5-20 Anson units per kg. 5. In a method for cleaning dishes, the step comprising applying to the dishes an aqueous solution of a dishwashing composition having a pH of 7-9 at a concentration of 3 g. per litre in aqueous solution, said composition consisting essentially of 2-10% by weight of a nonionic synthetic detergent, from 40-60% of an alkali metal condensed phosphate, from 515% of an alkali metal silicate and amylolytic enzymes derived from bacteria or fungi in an amount such that the composition has an amylolytic activity of 10 -10 maltose units per kg.

6. The step according to claim 5, wherein the dishwashing composition contains in addition thereto proteolytic enzymes in an amount such that the composition has a proteolytic activity of 5-20 Anson units per kg.

References Cited UNITED STATES PATENTS 3,519,570 7/1970 McCarty 25289 3,679,589 7/1972 Schnegelberger et al.

252DIG 12 WILLIAM E. SCHULZ, Primary Examiner US. Cl. X.R. 252 

